1. ➢Capsule
➢Pili
➢Endospore R.Parvathi Devi,
M.Sc. Microbiology
Submitted to
Dr. K.Kavitha, Assistant Professor, PG and Research
Department of Microbiology, Sadakathullah Appa
College (Autonomous), Tirunelveli
2. CAPSULE
● Capsules are a types of Gelatinous covering
layer of entire bacterium.
● Well organized and not easily washed off.
● It is lies outside the cell envelope.
3. ● Both gram-negative and gram-positive bacteria
contain capsules.
● Observed under a light microscope by applying
negative stains or specific capsule stains.
● Contain water which protects the cells from
desiccation.
4. COMPOSITION
● Bacterial Capsules are made of polysaccharides
● Some species it is made of other materials,
● For example, the capsule of Bacillus anthracis is
made of poly-D-glutamic acid.
5. TYPES OF CAPSULE
Macro-capsule
● The thickness of the Macro-capsule is 0.2µm or more.
● Visible under a light microscope.
Microcapsule
• The thickness of the Microcapsule is
0.2µm.
• Visible under Electron microscope.
6. FUNCTIONS
● Virulence factor for pathogenic bacteria.
● anti-phagocytic.
● Prevents desiccation of cell.
● Protects the cell from benign dry.
● Same charged capsule they repel.
● Defends: physical pressure and chemical damage.
● Prevent: bacteriophage from being attached to the cell surface.
● Nutrient supply is low in the cell it functions as a source of nutrition.
7. PILI
● Shorter than flagella.
● More in number.
● Bacterial conjugation, attachment to the surface and
motility.
● They are present in both Gram-positive and Gram-
negative More prevalent in Gram-negative bacteria.
● Made up of an oligomeric protein known as pilin.
8. STRUCTURE
● Shorter than flagella.
● The length is ~0.5 𝝁m and thickness is ~10 nm
● Originate from the cytoplasmic membrane.
● They are present on motile as well as non-motile cells.
● Sex pili are a special type of fimbriae, (up to 10 in each cell)
9. FUNCTION
CONJUGATION PILI
● Referred to as the appendages.
● Involved in the conjugation.
● Cell to cell attachment during conjugation for DNA transfer.
● They are also termed as “sex pili” as they facilitate gene transfer
and recombination in the bacterial cell.
● It is a primitive mode of sexual reproduction in bacteria.
10. TYPE IV PILI
● They are responsible for the twitching motility.
● They adhere to the surface and bring about the
movement by contraction.
● Many archaea contain this type of pili
● which help them to adhere to various surfaces
11. ENDOSPORE
● Surviving for many years while still preserving the genetic
material of bacteria.
● Once the conditions are favorable, these spores get
reactivated and germinate.
● The most common bacteria that form endospores
are Bacillus and Clostridium species.
12. ● Appears as a round cell within the vegetative
or the mother cell.
● Their position inside the mother cell varies
from one bacterium to the other.
● Positioned at the center, terminal or
subterminal
13. STRUCTURE
EXOSPORIUM: Outer covering that is thin
and delicate.
CORTEX: made up of the spore
peptidoglycan.
INNER MEMBRANE: permeability barrier
protecting the bacteria against damage-
causing chemicals.
CORE: centre & contains the genetic
information of the bacteria.
14. FUNCTION
● Beneficial to bacteria that produce them since they
ensure their survival during adverse conditions.
● Preserve the genetic material of bacteria for a very long
time.
● The resistant properties of endospores to heat, chemicals,
radiation, and desiccation lower the bacteria DNA
degradation.
● These endospores later germinate upon favorable
environmental conditions
